1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine and a printer.
2. Description of the Related Art
An image forming apparatus comprising, as members for forming an image on a recording material, a conveyance unit configured to convey a recording material, an image forming unit configured to form an image on a recording material, and a fixing unit configured to fix the image onto the recording material is known. Some image forming apparatus have such a configuration that a motor as a drive source for driving members for forming an image on a recording material is mounted on a metal plate (plate-like meta member) as a frame of an apparatus body of the image forming apparatus. The drive source becomes a vibrating source which vibrates when the drive source causes a member for forming an image on a recording material to drive upon forming the image. Transmission of the vibration from the drive source to a metal plate causes the metal plate to vibrate, which may generate a noise.
The drive source is provided with various devices to decrease the noise which is generated upon forming an image. Japanese Patent Laid-open Publication No. 2009-009016 discusses a configuration that holes are provided in an area of a metal plate which vibrates most in order to decrease the noise generated from the metal plate on which the drive motor is mounted. Japanese Patent Laid-open Publication No. 2009-031347 discusses a configuration that holes are provided in a frame facing to an exterior cover to prevent a noise which is reflected by the exterior cover to be directed to the frame within the apparatus body from further being reflected by the frame and directing to an exterior member.
However, the above described conventional image forming apparatus has a following problem. In a case where the holes are provided in the area most vibrating in the plate as it is discussed in Japanese Patent Laid-open Publication No. 2009-009016, the noise having a specific frequency can be decreased but the noise having a frequency other than the specific frequency can be hardly decreased. Therefore, in a case where the noise has a wide frequency range, the noise cannot be decreased to a satisfactory level.
In Japanese Patent Laid-open Publication No. 2009-031347, holes are provided in the frame in order to control the noise which is reflected by the exterior cover and directed to the frame so as not to be further reflected by the frame. In other words, the holes are not provided in order to decrease a sound wave itself, which becomes the noise, in the sound waves generated from the frame. Therefore, in a case where holes such as intake ports and exhaust ports are provided in the exterior cover, the noise may come out of the apparatus body and thus positions of the holes provided in the exterior cover are constrained. Depending on a configuration inside the apparatus body, the noise may come out of the apparatus body through an exterior member such that the noise, which is reflected by the exterior cover to be directed to the frame, passes through the holes of the frame and is subsequently reflected by the other member disposed inside the frame within the apparatus body to be directed to the exterior cover again.